Question

cos(x/3)cos(x/3)=(1/2)(1+cos(2/3)) true or false? i really have no idea!!!

Answer 1

Did you mean to write this?\[\large \cos\left(\frac{x}{3}\right)\cos\left(\frac{x}{3}\right)=\frac{1}{2}\left[1+\cos\left(\frac{2x}{3}\right)\right]\]

There is no x on the right side of your equation, so I wanted to see if this is what you meant to write.

Answer 2

Yes! thankyou

Answer 3

Here is our `Half Angle Formula for Cosine`:\[\large \cos^2 \theta=\frac{1}{2}\left[1+\cos2\theta\right]\]A good one to remember.
Hmmmmmm, does it look like the rule is being followed in this case?
Think about it a sec! :)

Answer 4

yeah...haha

Answer 5

Yah it looks like it's true doesn't it?? :O
Our angle is x/3 in this case.
It appears to be twice that angle on the right.. I think we have a winner!

Answer 6

Thank you so much!

Answer 7

give him a medal atleast geez.